1. Field of the Invention
The present invention relates generally to medical methods and devices. More particularly, the invention relates to methods and devices for circulatory valve repair, especially for the repair of heart valves, such as repair of the mitral or tricuspid valve for treating mitral or tricuspid regurgitation.
Four valves in the heart direct blood flow through the heart in a forward direction. On the left side of the heart, the mitral and aortic valves direct oxygenated blood from the lungs to the aorta for distribution to the body. On the right side of the heart, the tricuspid and pulmonary valves direct de-oxygenated blood from the body to the pulmonary arteries for distribution to the lungs.
The four heart valves consist of moveable leaflets that open and close in response to differential pressures on either side of the valve. The mitral valve, for example, has two leaflets while the tricuspid valve has three. The components of the mitral valve assembly include a mitral valve annulus, an anterior leaflet, a posterior leaflet, two papillary muscles which are attached at their bases to the interior surface of the left ventricular wall, and multiple chordae tendineae, which are cord-like structures that couple the mitral valve leaflets to the papillary muscles. The other heart valves have similar supporting structures, though each is somewhat unique.
If a functional problem occurs in one or more heart valves, cardiac function is often adversely affected. Such valve problems may be classified as either stenosis, in which a valve does not open properly, or insufficiency (also known as regurgitation), in which a valve does not close properly. Mitral regurgitation, for example, is typically caused by dysfunction of the mitral annulus, subvalvular apparatus, or direct injury to the valve leaflets. Severe mitral regurgitation is a serious problem which, if left untreated, can adversely affect cardiac function and compromise a patient's quality of life and longevity. In cases where an atrioventricular valve becomes regurgitant due to damage to the valve supporting structures, papillary muscles, leaflets or annular geometry, the fraction of blood in the ventricle that is actually moved forward with each beat is reduced. To compensate, the ventricular cavity enlarges in an attempt to maintain forward output. By enlarging, the heart attempts to maintain the same absolute volume of forward flow by ejecting a reduced percentage of a larger volume. This enlargement of the ventricle is accompanied by an enlargement of the supporting structures and annulus of the valve, resulting in separation of the valve leaflets at their point of co-aptation during ventricular systole and further leaking of blood retrograde across the valve. This continues the cycle of ventricular enlargement, annular dilatation and regurgitation and subsequent loss of forward output and progressive heart failure. Other heart valve problems often cause similarly grave sequelae.
Treatment of heart valve stenosis or regurgitation, such as mitral or tricuspid regurgitation, often involves an open-heart surgical procedure to replace or repair the valve. Repair of a regurgitant valve such as the mitral valve is often performed in preference to replacement. Such procedures generally require a large incision into the thorax of the patient (a thoracotomy), sometimes requiring a median sternotomy (cutting through the middle of the sternum). Such procedures routinely include a corrective procedure called an annuloplasty, designed to restore the valve annulus shape, strengthen the annulus, and allow better leaflet co-aptation as a part of the repair. Such open heart procedures also usually involve placing the patient on a cardiopulmonary bypass machine for sustained periods so that the patient's heart and lungs can be artificially stopped during the procedure. Finally, valve repair and replacement procedures are typically technically challenging and require that a relatively large incision be made through the wall of the heart to access the valve. Due to the highly invasive nature of open heart valve repair or replacement, many patients, such as elderly patients, patients having recently undergone other surgical procedures, patients with comorbid medical conditions, children, late-stage heart failure patients and the like, are often considered too high-risk to undergo heart valve surgery and are committed to progressive deterioration and cardiac enlargement. Often, such patients have no feasible alternative treatments for their heart valve conditions.
Therefore, it would be advantageous to have methods and devices for repairing a mitral valve to treat mitral regurgitation in a less invasive manner than is available through current techniques. In some instances, it may be advantageous to provide for repair of a mitral valve, as well as other heart valves, through minimally invasive incisions or intravascularly. In other cases, it may be beneficial to use improved devices and methods in an open heart surgical procedure, on either a beating heart or a stopped heart. In beating heart procedures, including both minimally invasive and intravascular access procedures, it would be useful to provide for stabilization of the valve annulus while any procedure is being performed. In such beating heart procedures, it would be further useful to provide systems for the direct observation of the valve annulus from within a heart chamber to facilitate performing desired interventions. Moreover, it would be still further desirable if the apparatus and systems of the present invention were useful for treating not only the annulus of heart valves, but also other natural and created holes in tissue which require strengthening or closing. Improved devices and methods would ideally be relatively simple and easy to use and would enable durable, long-lasting mitral valve repair, either in a minimally invasive or open heart procedure, for many patients who are not candidates for more conventional procedures. At least some of these objectives will be met by the present invention.
2. Description of the Background Art
Published U.S. Application 2002/0163784A12 describes a port for providing access to a beating heart to perform diagnostic and therapeutic procedures, including a stapled annuloplasty procedure. Published U.S. Application 2002/0042621 describes a heart valve annuloplasty system with constrictable plication bands which are optionally attached to a linkage strip. Published U.S. Application 2002/0087169 describes a remote controlled catheter system which can be used to deliver anchors and a tether for performing an annuloplasty procedure. Other patent publications of interest include WO01/26586; US2001/0005787; US2001/0014800; US2002/0013621; US2002/0029080; US2002/0035361; US2002/0042621; US2002/0095167; and US2003/0074012. U.S. Pat. Nos. of interest include 4,014,492; 4,042,979; 4,043,504; 4,055,861; 4,700,250; 5,366,479; 5,450,860; 5,571,215; 5,674,279; 5,709,695; 5,752,518; 5,848,969; 5,860,992; 5,904,651; 5,961,539; 5,972,004; 6,165,183; 6,197,017; 6,250,308; 6,260,552; 6,283,993; 6,269,819; 6,312,447; 6,332,893; and 6,524,338. Publications of interest include De Simone et al. (1993) Am. J. Cardiol. 73:721-722 and Downing et al. (2001) Heart Surgery Forum, Abstract 7025.